This invention pertains to an oil pump, and more particularly to an oil pump for use in a horizontal rotary compressor.
In some compressors, the crankshaft is vertically disposed in the compressor housing and has its lower end portion submerged in an oil sump. A helical groove is provided in the crankshaft, and upon rotation of the crankshaft by the motor, oil is delivered upwardly through the groove along the crankshaft for lubricating bearings and other moving parts. Generally, some type of impeller means is also provided at the lower end of the crankshaft to assist in urging oil upwardly through the helical groove.
In contrast to the above compressors wherein oil is delivered upwardly by a helical groove in the vertically mounted crankshaft, the crankshaft in a horizontal piston or rotary compressor cannot directly elevate the oil upwardly through a helical groove in the crankshaft. This has posed numerous problems in properly lubricating bearings and other moving parts in a horizontally disposed compressor. The fact that such horizontal compressors are presently in use indicates that some means have been provided in the prior art to deliver lubricant to a rotating horizontal crankshaft, however, problems continue to exist in adequately lubricating bearings and moving parts, as well as an inability to adequately self-prime the oil pump during start-up.
One earlier method for delivering lubricant upwardly to a rotating horizontal crankshaft uses a disc or plate attached to the crankshaft to rotate therewith and which has its lower portion disposed in the oil sump. A circular groove is provided in the flat surfaces of the disc, and upon rotation of the crankshaft, the disc rotates through the oil sump and carries lubricant in the grooves upwardly to a cavity or chamber adjacent the crankshaft. The lubricant is then delivered from the chamber by means of a series of passages to the crankshaft for lubricating bearings. Several drawbacks exist with this type of oil pump, one of the drawbacks being the inability to deliver a desired amount of lubricant to the crankshaft and associated bearings. Other drawbacks include additional expense in materials and labor in providing the grooved disc and a chamber in the crankcase with oil passages leading to the crankshaft and bearings.
Another type of oil pump for use with horizontal motor-compressor units utilizes a wick device disposed in the oil sump and in contact along several axial points of the crankshaft. The wick device delivers oil upwardly from the oil sump and through the wick to the crankshaft for further delivery along the crankshaft and bearings. An obvious drawback with this type of oiling device is that the wick may shrink down away from the crankshaft during prolonged use, thereby preventing proper lubrication of the crankshaft and bearings. Moreover, small pieces of the wick may eventually break off and clog oil passages or lodge between moving parts preventing proper movement.
In yet another type of horizontal compressor, a portion of the crankcase is submerged in the oil sump and has a passageway leading from the oil sump upwardly to a chamber provided between an eccentric reduced portion of the crankshaft and crankcase. Rotation of the crankshaft causes oil to be drawn upwardly through the crankcase passageway into the chamber and through an axially extending passage in the crankshaft. One of the problems associated with this particular type of oil pump is that the axially extending passage in communication with the chamber does not fully utilize the centrifugal force of the rotating crankshaft to efficiently deliver desired amounts of lubrication along the crankshaft for lubricating bearings.
In still another type of oil pump system for a rotating horizontal shaft, the center portion of the shaft is enlarged and tapers radially inwardly toward the remote ends. A pair of oppositely angularly disposed helical grooves are provided on the respective tapering surfaces of the enlarged center portion and have their axially outermost ends in communication with an oil supply. Upon rotation of the shaft and helical grooves therein, oil is delivered axially inwardly along the grooves to the center of the shaft for lubrication thereof. One of the undesired features with this type of oil pump is that the oil supply is required to be disposed at the same height as the ends of the rotating horizontal shaft. In virtually all horizontal rotary compressors, the crankshaft is disposed above the surface of the oil sump in the compressor housing.
In view of the above, it is quite clear that a need still exists for an oil pump in a horizontal motor-compressor unit that efficiently delivers lubricant upwardly to the crankshaft and horizontally along its length for proper lubrication of bearings and other moving parts, and which has a self-priming feature.